1. Field of the Invention
The present invention relates to a picture data transmission device for use in transmitting a picture in a television system and, more particularly, to a picture data transmission device for use as a transmission terminal device in a television conference system and a picture signal coding method thereof.
2. Description of the Related Art
In a television conference system in which a conference is held using a two-way television system, a conventional picture data transmission device for transmitting picture data codes the entire image obtained by a camera and transmits the coded image to a terminal device of other conference participant. FIG. 6 shows an example of a structure of a conventional picture data transmission device.
With reference to FIG. 6, a conventional picture data transmission device 100 includes a picture input circuit 101 for receiving input of a picture signal, a picture coding circuit 102 for coding a picture applied through the picture input circuit 101 and a network interface circuit 103 for transmitting a coded signal obtained by the picture coding circuit 102 to a terminal device of other conference participant through an ISDN network 120.
A picture signal obtained by a camera 110 is applied to the picture data transmission device 100 through the picture input circuit 101 and subjected to compression and coding processing conducted by the picture coding circuit 102. Then, the generated coded data is output from the network interface circuit 103 and transmitted to other terminal device through the ISDN network 120.
At the coding of a picture signal, thus structured picture data transmission device conventionally codes the entire image on an image basis. In the transmission of a signal over an ISDN network, however, because a transmission speed is not high enough, coding of a picture signal of a picture with rapid motions requires frame-dropping to be executed and a quantization unit to be increased in order to suppress an increase in the amount of coded data generated.
However, in a case where a picture as a background of an object to be filmed (hereinafter, referred to as a background picture) is a picture which is steadily moving and whose motion is more rapid than that of a picture of the object to be filmed itself (hereinafter, referred to as a target picture), frame-cutdown and rough quantization will make the target picture unclear.
Another method of reducing the amount of coded data generated is extracting a predetermined region 150 out of an original picture frame 140 prior to coding processing to make the other region 160 unicolor (e.g. all in black), thereby drastically reducing coded data of the other region 160 in question as illustrated in FIG. 7. This method, however, results in making the other region 160 in question unicolor only to make the contents of the picture of the other region 160 completely unknown.
As described above, conventional picture data transmission devices code the entire image at the time of coding a picture signal. Then, with respect to a picture with rapid motions, frame-dropping and rough quantization are conducted to suppress an increase in the amount of coded data generated, whereby also when a background picture is more rapid in motion than a target picture, the target picture becomes unclear.
Also when the amount of coded data generated is reduced by extracting a predetermined region out of a picture frame and making the remaining region unicolor, a picture of other region than the predetermined region in question can not be transmitted.
An object of the present invention is to provide a picture data transmission device which solves the above-described conventional shortcomings and is capable of transmitting a clear picture with the amount of coded data generated suppressed without having frame-dropping and an increase in a quantization unit and without limiting a region subjected to coding processing, and a picture signal coding method thereof.
According to the first aspect of the invention, a picture data transmission device for use in the transmission of a picture in a television system, comprises
picture input means for receiving input of a picture signal,
region extraction processing means for extracting, from a picture signal applied through the picture input means, a picture signal of a predetermined region in a picture frame of the picture in question,
picture coding means for coding and outputting a picture signal of a region extracted by the region extraction processing means, and
interface means for transmitting a coded signal obtained by coding by the picture coding means to a terminal device of other conference participant by means of predetermined transmission means, wherein
the region extraction processing means
out of a picture frame, extracts a picture signal of a target picture region containing a target picture and a picture signal of a part of a background region which is other region than the target picture region in question and transfers the signals to the picture coding means, and
selects a part of the background region to be extracted from the picture signal such that the part varies with each picture frame.
In the preferred construction, with respect to each picture frame, the region extraction processing means sequentially selects an arbitrary number of divisional background regions which are obtained by dividing the background region into a plurality of small regions to extract a picture signal.
In another preferred construction, the picture coding means outputs a coded signal obtained by coding a picture signal extracted by the region extraction processing means, as well as continuously outputting a coded signal output immediately before with respect to a region in the picture frame not included in the picture signal extracted by the region extraction processing means.
In another preferred construction, with respect to each picture frame, the region extraction processing means sequentially selects an arbitrary number of divisional background regions which are obtained by dividing the background region into a plurality of small regions to extract a picture signal, and the picture coding means outputs a coded signal obtained by coding a picture signal extracted by the region extraction processing means, as well as continuously outputting a coded signal output immediately before with respect to a region in the picture frame not included in the picture signal extracted by the region extraction processing means.
According to the second aspect of the invention, a picture signal coding method in a television system, comprising the steps of
from an applied picture signal, extracting a picture signal of a predetermined region in a picture frame of the picture in question, and
coding and outputting a picture signal of a region extracted by the region extraction step, wherein
at the region extraction step
out of a picture frame, a picture signal of a target picture region containing a target picture and a picture signal of a part of a background region which is other region than the target picture region in question are extracted and transferred to the picture coding means, and
a part of the background region to be extracted from the picture signal is selected such that the part varies with each picture frame.
In the preferred construction, at the region extraction step, with respect to each picture frame, an arbitrary number of divisional background regions which are obtained by dividing the background region into a plurality of small regions are sequentially selected to extract a picture signal.
In another preferred construction, at the coded signal outputting step, a coded signal obtained by coding a picture signal extracted at the region extraction step is output, while a coded signal output immediately before is continuously output with respect to a region in the picture frame not included in the picture signal extracted at the region extraction step.
In another preferred construction, at the region extraction step, an arbitrary number of divisional background regions which are obtained by dividing the background region into a plurality of small regions are sequentially selected with respect to each picture frame to extract a picture signal, and at the coded signal outputting step, a coded signal obtained by coding a picture signal extracted at the region extraction step is output, while a coded signal output immediately before is continuously output with respect to a region in the picture frame not included in the picture signal extracted at the region extraction step.
According to the third aspect of the invention, a computer readable memory storing a picture signal coding program for controlling a picture data transmission device for use in the transmission of a picture in a television system to code a picture signal,
the picture signal coding program comprising the steps of
from an applied picture signal, extracting a picture signal of a predetermined region in a picture frame of the picture in question, and
coding and outputting a picture signal of a region extracted at the region extraction step, wherein
at the region extraction step
out of a picture frame, a picture signal of a target picture region containing a target picture and a picture signal of a part of a background region which is other region than the target picture region in question are extracted and transferred to the picture coding means, and
a part of the background region to be extracted from the picture signal is selected such that the part varies with each picture frame.
In the preferred construction, the picture signal coding program, at the region extraction step, sequentially selects, with respect to each picture frame, an arbitrary number of divisional background regions which are obtained by dividing the background region into a plurality of small regions to extract a picture signal.
In another preferred construction, the picture signal coding program, at the coded signal outputting step, outputs a coded signal obtained by coding a picture signal extracted at the region extraction step, as well as continuously outputting a coded signal output immediately before with respect to a region in the picture frame not included in the picture signal extracted at the region extraction step.
In another preferred construction, the picture signal coding program, at the region extraction step, with respect to each picture frame, sequentially selects an arbitrary number of divisional background regions which are obtained by dividing the background region into a plurality of small regions to extract a picture signal, and at the coded signal outputting step, outputs a coded signal obtained by coding a picture signal extracted at the region extraction step, as well as continuously outputting a coded signal output immediately before with respect to a region in the picture frame not included in the picture signal extracted at the region extraction step.
According to another aspect of the invention, a picture data transmission device for use in the transmission of a picture in a television system, comprises
a picture input circuit which receives input of a picture signal,
a region extraction processing circuit which extracts, from a picture signal applied through the picture input circuit, a picture signal of a predetermined region in a picture frame of the picture in question,
a picture coding circuit which codes and outputs a picture signal of a region extracted by the region extraction processing circuit, and
an interface circuit which transmits a coded signal obtained by coding by the picture coding circuit to a terminal device of other conference participant by means of a predetermined transmission circuit, wherein
the region extraction processing circuit
out of a picture frame, extracts a picture signal of a target picture region containing a target picture and a picture signal of a part of a background region which is other region than the target picture region in question and transfers the signals to the picture coding circuit, and
selects a part of the background region to be extracted from the picture signal such that the part varies with each picture frame.
Other objects, features and advantages of the present invention will become clear from the detailed description given herebelow.